JP6965736B2 - Air conditioner - Google Patents

Description

The present invention relates to an air conditioner that performs a reverse cycle defrosting operation during a heating operation.

When the air conditioner is heated when the outside air temperature is low, frost is generated in the outdoor heat exchanger that functions as an evaporator. The frost generated in the outdoor heat exchanger during the heating operation is melted by performing the reverse cycle defrosting operation. The frost is then discharged as drain water through the bottom plate of the outdoor unit located below the outdoor heat exchanger. When performing the reverse cycle defrosting operation, the air conditioner stops the outdoor fan and switches the refrigerating cycle from the heating cycle to the cooling cycle. Then, the air conditioner causes the refrigerant compressed by the compressor to have a high temperature to flow into the outdoor heat exchanger. As a result, the outdoor heat exchanger is heated and the frost generated in the outdoor heat exchanger is melted.

By the way, when the heating operation is performed when the outside air temperature is around 0 ° C., the air passing through the outdoor heat exchanger becomes 0 ° C. or less and hits the outdoor fan. Further, when the outdoor heat exchanger is clogged with frost generated in the outdoor heat exchanger and air cannot pass through, the air that does not pass through the outdoor heat exchanger that has flowed in from the outlet hits the outdoor fan. As a result, frost may be generated not only on the outdoor heat exchanger but also on the outdoor fan.

The frost generated in the outdoor fan cannot be melted by the reverse cycle defrosting operation described above, which is executed by stopping the outdoor fan. Therefore, an air conditioner that performs fan defrosting operation to melt the frost generated by the outdoor fan has been proposed. For example, in the air conditioner shown in Patent Document 1, after the reverse cycle defrosting operation is performed to defrost the outdoor heat exchanger, the refrigerant discharged from the compressor remains flowing into the outdoor heat exchanger. It is described that the outdoor fan is rotated for a certain period of time. As a result, warm air heated by the outdoor heat exchanger can be applied to the outdoor fan to melt the frost generated by the outdoor fan.

JP-A-2010-121789

In the air conditioner shown in Patent Document 1, the defrosting operation of the outdoor heat exchanger and the defrosting operation of the fan are performed at a predetermined operation time and at a predetermined number of rotations of the outdoor fan. If the outside air temperature is low during the fan defrosting operation, the temperature of the outdoor heat exchanger tends to drop. In addition, if the amount of frost generated in the outdoor heat exchanger at the start of the reverse cycle defrosting operation is large, a large amount of heat is consumed to melt the frost during the reverse cycle defrosting operation, so the fan defrosting operation is started. At that time, the temperature of the outdoor heat exchanger becomes low. When the outdoor fan is driven in such a situation, the temperature of the air in the vicinity of the outdoor fan immediately drops to below the melting temperature (0 ° C) of the frost generated in the outdoor fan, and defrosting cannot be performed. Problems arise.

The present invention solves the above-mentioned problems, and an object of the present invention is to provide an air conditioner that reliably melts frost generated in an outdoor fan by a fan defrosting operation.

In order to solve the above problems, the air conditioner of the present invention includes a refrigerant circuit in which refrigerant circulates in the order of a compressor, an indoor heat exchanger, an expansion valve, and an outdoor heat exchanger during heating operation, and the refrigerant circuit. Detects the flow path switching means for switching the flow direction of the refrigerant discharged from the compressor, the outdoor fan for blowing air to the outdoor heat exchanger, and the outdoor heat exchange temperature which is the temperature of the outdoor heat exchanger. The outdoor heat exchange temperature means is provided, and the outdoor fan is stopped during the heating operation, and the flow path switching means is switched to direct the refrigerant discharged from the compressor to the outdoor heat exchanger. After the defrosting operation and the heat exchange defrosting operation are completed, the outdoor fan is driven to defrost the outdoor fan while the refrigerant discharged from the compressor is directed to the outdoor heat exchanger. It has a control means for performing a fan defrosting operation. During the fan defrosting operation, the control means raises the temperature of the outdoor heat exchanger when the air temperature in the vicinity of the fan, which is the temperature of the air in the vicinity of the outdoor fan, becomes equal to or lower than the first threshold value. Perform ascending control.

According to the air conditioner of the present invention configured as described above, when the air temperature near the fan, which is the air temperature near the outdoor fan, becomes equal to or less than the first threshold value during the fan defrosting operation, the temperature of the outdoor heat exchanger The outdoor heat exchange temperature rise control is performed to raise the outdoor heat exchange temperature. As a result, the frost generated in the outdoor fan can be more reliably melted during the fan defrosting operation.

It is explanatory drawing of the air conditioner in embodiment of this invention, (A) is a refrigerant circuit diagram, (B) is a block diagram of an outdoor unit control means. It is a fan defrost control table in embodiment of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. As an embodiment, an air conditioner in which an outdoor unit and an indoor unit are connected by two refrigerant pipes will be described as an example. The present invention is not limited to the following embodiments, and various modifications can be made without departing from the gist of the present invention.

As shown in FIG. 1A, the air conditioner 1 in the present embodiment has an outdoor unit 2 installed outdoors and an indoor unit installed indoors and connected to the outdoor unit 2 by a liquid pipe 4 and a gas pipe 5. It is equipped with a machine 3. Specifically, the closing valve 25 of the outdoor unit 2 and the liquid pipe connecting portion 33 of the indoor unit 3 are connected by the liquid pipe 4. Further, the closing valve 26 of the outdoor unit 2 and the gas pipe connecting portion 34 of the indoor unit 3 are connected by the gas pipe 5. As a result, the refrigerant circuit 10 of the air conditioner 1 is formed.

<Outdoor unit configuration>
First, the outdoor unit 2 will be described. The outdoor unit 2 includes a compressor 21, a four-way valve 22, an outdoor heat exchanger 23, an expansion valve 24, a closing valve 25 to which the liquid pipe 4 is connected, and a closing valve 26 to which the gas pipe 5 is connected. , Equipped with an outdoor fan 27. Then, each of these devices except the outdoor fan 27 is connected to each other by each refrigerant pipe described later to form an outdoor unit refrigerant circuit 10a forming a part of the refrigerant circuit 10.

The compressor 21 is a variable capacity compressor whose operating capacity can be changed by controlling the rotation speed by an inverter (not shown). The refrigerant discharge side of the compressor 21 is connected to the port a of the four-way valve 22 by a discharge pipe 61. Further, the refrigerant suction side of the compressor 21 is connected to the port c of the four-way valve 22 by a suction pipe 66.

The four-way valve 22 is a valve for switching the flow direction of the refrigerant, and includes four ports a, b, c, and d. As described above, the port a is connected to the refrigerant discharge side of the compressor 21 by a discharge pipe 61. The port b is connected to one of the refrigerant inlets and outlets of the outdoor heat exchanger 23 by a refrigerant pipe 62. As described above, the port c is connected to the refrigerant suction side of the compressor 21 by a suction pipe 66. The port d is connected to the closing valve 26 by an outdoor unit gas pipe 64. The four-way valve 22 is the flow path switching means of the present invention.

The outdoor heat exchanger 23 exchanges heat between the refrigerant and the outside air taken into the outdoor unit 2 by the rotation of the outdoor fan 27 described later. As described above, one refrigerant inlet / outlet of the outdoor heat exchanger 23 is connected to the port b of the four-way valve 22 by the refrigerant pipe 62, and the other refrigerant inlet / outlet is connected to the closing valve 25 by the outdoor unit liquid pipe 63. The outdoor heat exchanger 23 functions as a condenser during the cooling operation and as an evaporator during the heating operation by switching the four-way valve 22 described later.

The expansion valve 24 is an electronic expansion valve driven by a pulse motor (not shown). Specifically, the opening degree is adjusted by the number of pulses applied to the pulse motor. The opening degree of the expansion valve 24 is adjusted so that the discharge temperature, which is the temperature of the refrigerant discharged from the compressor 21, becomes a predetermined target temperature during the heating operation. Further, the opening degree of the expansion valve 24 is adjusted so that the refrigerant supercooling degree on the refrigerant outlet side of the indoor heat exchanger 31, which will be described later, which functions as a condenser during the cooling operation, becomes a predetermined target supercooling degree. NS.

The outdoor fan 27 is made of a resin material and is arranged in the vicinity of the outdoor heat exchanger 23. The central portion of the outdoor fan 27 is connected to a rotating shaft (not shown) of the fan motor 27a. The rotation of the fan motor 27a causes the outdoor fan 27 to rotate. By the rotation of the outdoor fan 27, the outside air is taken into the inside of the outdoor unit 2 from the suction port (not shown) of the outdoor unit 2, and the outside air heat exchanged with the refrigerant in the outdoor heat exchanger 23 is taken out from the air outlet (not shown) of the outdoor unit 2. Machine 2 Release to the outside.

In addition to the configuration described above, the outdoor unit 2 is provided with various sensors. As shown in FIG. 1A, the discharge pipe 61 has a discharge pressure sensor 71 that detects the pressure of the refrigerant discharged from the compressor 21, and the temperature of the refrigerant discharged from the compressor 21 (the discharge temperature described above). ) Is provided as a discharge temperature sensor 73. The suction pipe 66 is provided with a suction pressure sensor 72 that detects the pressure of the refrigerant sucked into the compressor 21, and a suction temperature sensor 74 that detects the temperature of the refrigerant sucked into the compressor 21.

A heat exchange temperature sensor 75 that detects the outdoor heat exchange temperature, which is the temperature of the outdoor heat exchanger 23, is provided in a substantially intermediate portion of the refrigerant path (not shown) of the outdoor heat exchanger 23. An outside air temperature sensor 76 for detecting the temperature of the outside air flowing into the inside of the outdoor unit 2, that is, the outside air temperature is provided in the vicinity of the suction port (not shown) of the outdoor unit 2.

Further, the outdoor unit 2 is provided with an outdoor unit control means 200. The outdoor unit control means 200 is mounted on a control board housed in an electrical component box (not shown) of the outdoor unit 2. As shown in FIG. 1B, the outdoor unit control means 200 includes a CPU 210, a storage unit 220, a communication unit 230, and a sensor input unit 240.

The storage unit 220 is composed of a flash memory, and stores the control program of the outdoor unit 2, the detection value corresponding to the detection signals from various sensors, the control state of the compressor 21, the outdoor fan 27, and the like. Although not shown, the storage unit 220 stores in advance a rotation speed table in which the rotation speed of the compressor 21 is determined according to the required capacity received from the indoor unit 3.

The communication unit 230 is an interface for communicating with the indoor unit 3. The sensor input unit 240 captures the detection results of the various sensors of the outdoor unit 2 and outputs them to the CPU 210.

The CPU 210 captures the detection results of each sensor of the outdoor unit 2 described above via the sensor input unit 240. Further, the CPU 210 captures the control signal transmitted from the indoor unit 3 via the communication unit 230. The CPU 210 controls the drive of the compressor 21 and the outdoor fan 27 based on the captured detection result, control signal, and the like. Further, the CPU 210 controls the switching of the four-way valve 22 based on the captured detection result and the control signal. Further, the CPU 210 adjusts the opening degree of the expansion valve 24 based on the captured detection result and the control signal.

<Composition of indoor unit>
Next, the indoor unit 3 will be described with reference to FIG. 1 (A). The indoor unit 3 includes an indoor heat exchanger 31, an indoor fan 32, a liquid pipe connecting portion 33 to which the other end of the liquid pipe 4 is connected, and a gas pipe connecting portion 34 to which the other end of the gas pipe 5 is connected. I have. Then, each of these devices except the indoor fan 32 is connected to each other by each refrigerant pipe described in detail below to form an indoor unit refrigerant circuit 10b forming a part of the refrigerant circuit 10.

The indoor heat exchanger 31 exchanges heat between the refrigerant and the indoor air taken into the indoor unit 3 from a suction port (not shown) of the indoor unit 3 by the rotation of the indoor fan 32 described later. One refrigerant inlet / outlet of the indoor heat exchanger 31 is connected to the liquid pipe connecting portion 33 by the indoor unit liquid pipe 67. The other refrigerant inlet / outlet of the indoor heat exchanger 31 is connected to the gas pipe connecting portion 34 by the indoor unit gas pipe 68. The indoor heat exchanger 31 functions as an evaporator when the indoor unit 3 performs a cooling operation, and functions as a condenser when the indoor unit 3 performs a heating operation. In the liquid pipe connecting portion 33 and the gas pipe connecting portion 34, each refrigerant pipe is connected by welding, flare nut, or the like.

The indoor fan 32 is made of a resin material and is arranged in the vicinity of the indoor heat exchanger 31. The indoor fan 32 is rotated by a fan motor (not shown) to take indoor air into the indoor unit 3 from a suction port (not shown) of the indoor unit 3 and exchange heat with the refrigerant in the indoor heat exchanger 31 to bring the indoor air into the room. Blow into the room from an outlet (not shown) of the machine 3.

In addition to the configuration described above, the indoor unit 3 is provided with various sensors. The indoor unit liquid pipe 67 is provided with a liquid side temperature sensor 77 that detects the temperature of the refrigerant flowing into or out of the indoor heat exchanger 31. The indoor unit gas pipe 68 is provided with a gas side temperature sensor 78 that detects the temperature of the refrigerant flowing out of the indoor heat exchanger 31 or flowing into the indoor heat exchanger 31. A room temperature sensor 79 that detects the temperature of the indoor air flowing into the indoor unit 3, that is, the room temperature, is provided in the vicinity of the suction port (not shown) of the indoor unit 3.

<Operation of refrigerant circuit>
Next, the flow of the refrigerant in the refrigerant circuit 10 and the operation of each part during the air conditioning operation of the air conditioner 1 in the present embodiment will be described with reference to FIG. 1 (A). In the following description, first, a case where the indoor unit 3 performs the heating operation will be described, and then a case where the indoor unit 3 will perform the cooling operation will be described. A case of performing a defrosting operation including a heat exchange defrosting operation for melting the frost generated in the outdoor heat exchanger 23 and a fan defrosting operation for melting the frost generated in the outdoor fan 27 will be described.

<Heating operation>
When the indoor unit 3 performs the heating operation, the CPU 210 communicates the four-way valve 22 with a solid line as shown in FIG. 1A, that is, the port a and the port d of the four-way valve 22 communicate with each other. Switch so that b and port c communicate with each other. As a result, the refrigerant circulates in the direction indicated by the solid arrow in the refrigerant circuit 10, and the outdoor heat exchanger 23 functions as an evaporator and the indoor heat exchanger 31 functions as a condenser.

The high-pressure refrigerant discharged from the compressor 21 flows through the discharge pipe 61 and flows into the four-way valve 22, flows from the four-way valve 22 through the outdoor unit gas pipe 64, and flows into the gas pipe 5 via the closing valve 26. .. The refrigerant flowing through the gas pipe 5 flows into the indoor unit 3 via the gas pipe connecting portion 34.

The refrigerant that has flowed into the indoor unit 3 flows through the indoor unit gas pipe 68 and flows into the indoor heat exchanger 31, and is condensed by exchanging heat with the indoor air taken into the indoor unit 3 by the rotation of the indoor fan 32. do. In this way, the indoor heat exchanger 31 functions as a condenser, and the indoor air that has exchanged heat with the refrigerant in the indoor heat exchanger 31 is blown into the room from an outlet (not shown), so that the indoor unit 3 is installed. The room is heated.

The refrigerant flowing out of the indoor heat exchanger 31 flows through the indoor unit liquid pipe 67 and flows into the liquid pipe 4 via the liquid pipe connecting portion 33. The refrigerant that has flowed through the liquid pipe 4 and has flowed into the outdoor unit 2 through the closing valve 25 is depressurized when it flows through the outdoor unit liquid pipe 63 and passes through the expansion valve 24. As described above, the opening degree of the expansion valve 24 during the heating operation is adjusted so that the discharge temperature of the compressor 21 becomes a predetermined target temperature.

The refrigerant that has passed through the expansion valve 24 and has flowed into the outdoor heat exchanger 23 exchanges heat with the outside air taken into the outdoor unit 2 by the rotation of the outdoor fan 27 and evaporates. The refrigerant flowing out from the outdoor heat exchanger 23 to the refrigerant pipe 62 flows through the four-way valve 22 and the suction pipe 66, is sucked into the compressor 21, and is compressed again.

<Cooling operation>
When the indoor unit 3 performs a cooling operation or a defrosting operation, the CPU 210 communicates the four-way valve 22 with a broken line as shown in FIG. 1A, that is, the port a and the port b of the four-way valve 22 communicate with each other. Also, switch so that port c and port d communicate with each other. As a result, the refrigerant circulates in the direction indicated by the broken arrow in the refrigerant circuit 10, and the outdoor heat exchanger 23 functions as a condenser and the indoor heat exchanger 31 functions as an evaporator.

The high-pressure refrigerant discharged from the compressor 21 flows through the discharge pipe 61 and flows into the four-way valve 22, and flows from the four-way valve 22 through the refrigerant pipe 62 and flows into the outdoor heat exchanger 23. The refrigerant flowing into the outdoor heat exchanger 23 exchanges heat with the outside air taken into the outdoor unit 2 by the rotation of the outdoor fan 27 and condenses.

The refrigerant flowing out of the outdoor heat exchanger 23 flows through the outdoor unit liquid pipe 63 and is depressurized when passing through the expansion valve 24. As described above, the opening degree of the expansion valve 24 during the cooling operation is adjusted so that the refrigerant supercooling degree on the refrigerant outlet side of the indoor heat exchanger 31 functioning as a condenser becomes a predetermined target supercooling degree. NS.

The refrigerant that has passed through the expansion valve 24 flows out to the liquid pipe 4 via the closing valve 25. The refrigerant that has flowed through the liquid pipe 4 and has flowed into the indoor unit 3 through the liquid pipe connecting portion 33 flows through the liquid pipe 67 of the indoor unit and flows into the indoor heat exchanger 31.

The refrigerant flowing into the indoor heat exchanger 31 evaporates by exchanging heat with the indoor air taken into the indoor unit 3 by the rotation of the indoor fan 32. In this way, the indoor heat exchanger 31 functions as an evaporator, and in the case of cooling operation, the indoor air that has exchanged heat with the refrigerant in the indoor heat exchanger 31 is blown into the room from an outlet (not shown). , The room in which the indoor unit 3 is installed is cooled.

The refrigerant flowing out of the indoor heat exchanger 31 flows through the indoor unit gas pipe 68 and flows out to the gas pipe 5 via the gas pipe connecting portion 34. The refrigerant flowing through the gas pipe 5 flows into the outdoor unit 2 through the closing valve 26, flows in the order of the outdoor unit gas pipe 64, the four-way valve 22, and the suction pipe 66, is sucked into the compressor 21, and is compressed again.

<Defrosting operation>
The defrosting operation includes a heat exchange defrosting operation that melts the frost generated in the outdoor heat exchanger 23 and a fan defrosting operation that melts the frost generated in the outdoor fan 27. In the heat exchange defrosting operation, the refrigerant circuit 10 is set to the cooling cycle described above, and the high-temperature refrigerant discharged from the compressor 21 is passed through the outdoor heat exchanger 23 with the outdoor fan 27 stopped, thereby causing outdoor heat. Melt the frost generated in the exchanger 23. Further, the fan defrosting operation is an operation performed following the heat exchange defrosting operation when the fan defrosting operation start condition described later is satisfied. In the fan defrosting operation, the refrigerant circuit 10 drives the outdoor fan 27 in the same cooling cycle as in the heat exchange defrosting operation.

It is an object of the present invention to maintain the temperature of the air in the vicinity of the outdoor fan 27 during the fan defrosting operation described above at a high temperature, and the specific method thereof will be described below.
In the following description, the flow of processing performed by the CPU 210 of the outdoor unit control means 200 during the defrosting operation will be described with reference to FIG. In the following description, the air temperature near the fan, which is the temperature of the air near the outdoor fan 27, is Tf (unit: ° C.), and the outdoor heat exchange temperature, which is the temperature of the outdoor heat exchanger 23 during the fan defrosting operation, is defined as Tf (unit: ° C.). Tc (unit: ° C.), the rotation speed of the compressor 21 during the fan defrosting operation is Rc (unit: rps), and the rotation speed of the outdoor fan 27 during the fan defrosting operation is Rfo (unit: rpm).

<Regarding the rotation speed control of the outdoor fan 27 during fan defrosting operation>
If the fan defrosting operation start condition is satisfied after the air conditioner 1 finishes the heat exchange defrosting operation, the air conditioner 1 performs the fan defrosting operation. The fan defrosting operation start condition is determined by conducting a test or the like in advance, and the amount of frost generated by the outdoor fan 27 is at a level that hinders the driving of the outdoor fan 27. Is shown. A specific example of the fan defrosting operation start condition is when the outside air temperature detected by the outside air temperature sensor 76 at the end of the heat exchange defrosting operation is −10 ° C. or higher and 5 ° C. or lower.

Immediately after starting the fan defrosting operation, the rotation speed Rc of the compressor 21 is a predetermined rotation speed (for example, 90 rps), and the rotation speed Rfo of the outdoor fan 27 is, for example, the lower limit rotation speed of the use range (for example, 90 rps). For example, 200 rpm). If the outside air temperature is low during the fan defrosting operation, the outdoor heat exchange temperature Tc tends to decrease. Further, if the amount of frost generated in the outdoor heat exchanger 23 at the start of the heat exchange defrosting operation is large, a large amount of heat is consumed to melt the frost during the heat exchange defrosting operation. The temperature of the outdoor heat exchange temperature Tc becomes low. When the outdoor fan 27 is driven in such a situation, the air temperature Tf in the vicinity of the fan immediately drops to the melting temperature (0 ° C.) or less of the frost generated in the outdoor fan 27, and defrosting cannot be performed. Occurs.

Therefore, in the present embodiment, in order to prevent the air temperature Tf near the fan from becoming lower than the melting temperature of the frost generated in the outdoor fan 27, the rotation speed of the outdoor fan 27 and the compressor 21 are adjusted according to the outdoor heat exchange temperature Tc. Adjust the number of rotations of.

<Processing flow during defrosting operation>
Next, using the flowchart shown in FIG. 3, a process executed by the CPU 210 of the outdoor unit control means 200 when performing the defrosting operation, that is, the heat exchange defrosting operation and the fan defrosting operation will be described. Since the flow of the refrigerant in the refrigerant circuit 100 when each of the above defrosting operations is performed is the same as that during the cooling operation described above, detailed description thereof will be omitted.

The flowchart shown in FIG. 2 shows the flow of processing when the CPU 210 performs the defrosting operation, where ST represents a step and the number following it represents a step number. Note that FIG. 3 mainly describes the processing related to the present invention, and other processing, for example, control of the refrigerant circuit 100 corresponding to the operating conditions such as the set temperature and the air volume instructed by the user, is performed on the air. The description of the general processing related to the air conditioner 1 is omitted.

The CPU 210 determines whether or not the defrosting operation start condition is satisfied during the heating operation (ST101). Here, the defrosting operation start condition is determined by conducting a test or the like in advance, and indicates that the amount of frost formed in the outdoor heat exchanger 23 is at a level that hinders the heating capacity. .. As a specific example of the defrosting operation start condition, the heating operation time (the time during which the heating operation is continued from the time when the air conditioner 1 is started in the heating operation or when the air conditioner 1 is returned to the heating operation from the defrosting operation). ) Has elapsed for 30 minutes or more, and the state in which the refrigerant temperature detected by the heat exchange temperature sensor 75 is 5 ° C. or more lower than the outside air temperature detected by the outside air temperature sensor 36 continues for 10 minutes or more, or the previous time. For example, when a predetermined time (eg, 180 minutes) has elapsed since the defrosting operation of the above was completed.

If the defrosting operation start condition is not satisfied (ST101-No), the CPU 210 continues the heating operation currently being performed (ST102). When the defrosting operation start condition is satisfied (ST101-Yes), the CPU 210 executes the heat exchange defrosting operation (ST103). In the heat exchange defrost operation, the CPU 210 stops the compressor 21 and the outdoor fan 27, switches the four-way valve 22, puts the refrigerant circuit 100 in the cooling operation state, and then starts the compressor 21 at a predetermined rotation speed. Then, the outdoor heat exchanger 23 is defrosted. During the heat exchange defrosting operation, the outdoor fan 27 and the indoor fan 32 are stopped. As a result, the refrigerant discharged from the compressor 21 and flowing into the outdoor heat exchanger 23 melts the frost generated in the outdoor heat exchanger 23. As described above, it is desirable that the predetermined rotation speed of the compressor 21 during the heat exchange defrosting operation is as high as possible (for example, 90 rps).

Next, the CPU 210 determines whether or not the heat exchange defrosting operation end condition is satisfied (ST104). Here, the heat exchange defrosting operation end condition is determined by conducting a test or the like in advance, and is a condition in which the frost generated in the outdoor heat exchanger 23 is considered to have melted. Specific examples of the conditions for ending the heat exchange defrosting operation include whether or not the temperature of the refrigerant flowing out of the outdoor heat exchanger 23 detected by the heat exchange temperature sensor 75 is 10 ° C. or higher, and the outdoor heat exchange defrosting. Whether or not a predetermined time (eg, 10 minutes) has passed since the start of operation.

If the heat exchange defrosting operation end condition is not satisfied (ST104-No), the CPU 210 returns the process to ST103 and continues the heat exchange defrosting operation. If the heat exchange defrosting operation end condition is satisfied (ST104-Yes), the CPU 210 determines whether or not the fan defrosting operation start condition is satisfied (ST105). Here, the fan defrosting operation start condition is determined by conducting a test or the like in advance, and the amount of frost generated in the outdoor fan 27 is a level that hinders the driving of the outdoor fan 27. It shows that. A specific example of the fan defrosting operation start condition is when the outside air temperature detected by the outside air temperature sensor 76 at the end of the heat exchange defrosting operation is −10 ° C. or higher and 5 ° C. or lower. If the fan defrosting operation start condition is not satisfied (ST105-No), that is, if the amount of frost generated by the outdoor fan 27 is at a level that does not interfere with the driving of the outdoor fan 27, the CPU 210 Proceed to ST111.

If the fan defrosting operation start condition is satisfied (ST105-Yes), that is, if the amount of frost generated by the outdoor fan 27 is at a level that hinders the driving of the indoor fan 27, the CPU 210 is outdoors. The fan 27 is driven at a predetermined rotation speed Rfop (ST106) to start the fan defrosting operation. Here, the predetermined rotation speed Rfop is stored in the storage unit 220 in advance, and is a low rotation speed that is known to melt the frost generated in the outdoor fan 27 in the fan defrosting operation. The predetermined rotation speed Rfop is, for example, the lower limit rotation speed of the usage range of the outdoor fan 27.

Next, the CPU 210 determines whether or not the air temperature Tf near the fan is equal to or less than the first threshold value Tct1 (ST107). The air temperature Tf near the fan may be a detection value of a temperature detecting means (not shown) installed near the outdoor fan 27, but a parameter correlating with the air temperature Tf near the fan may be used. For example, in the present embodiment, the outdoor heat exchange temperature Tc detected by the heat exchange temperature sensor 75 is read as the air temperature Tf near the fan, and the outdoor heat exchange temperature Tc detected by the heat exchange temperature sensor 75 is equal to or less than the first threshold value Tct1. Determine if it exists. The first threshold value Tct1 (unit: ° C.) is determined in advance by a test or the like and stored in the storage unit 220 of the outdoor unit control means 200, and when the air temperature Tf near the fan becomes near the melting temperature (0 ° C.). It is a possible temperature of the outdoor heat exchanger 23 (for example, 3 ° C.). If the outdoor heat exchange temperature Tc is not equal to or less than the first threshold value Tct1 (ST107-No), that is, if the outdoor heat exchange temperature Tc is a temperature sufficient to melt the frost, the CPU 210 proceeds to ST110.

When the outdoor heat exchange temperature Tc is equal to or less than the first threshold value Tct1 (ST107-Yes), the rotation speed Rfo of the outdoor fan 27 and the rotation speed Rc of the compressor 21 are adjusted (ST108). Specifically, when the air temperature Tf near the fan becomes close to the melting temperature, the frost becomes difficult to melt. Therefore, when the outdoor heat exchange temperature Tc becomes the first threshold Tct1 or less, the outdoor heat exchange temperature Tc needs to be increased. There is. In order to increase the outdoor heat exchange temperature Tc, the rotation speed Rfo of the outdoor fan 27 is decreased and the rotation speed Rc of the compressor is increased. The rotation speed of the outdoor fan 27 at the start of the fan defrosting operation is a predetermined rotation speed Rfop, and since the predetermined rotation speed Rfop is the lower limit rotation speed of the usage range of the outdoor fan 27, a lower rotation speed is set here. Since the rotation speed is extremely low so that it is not used during normal operation, the air volume becomes unstable, but there is no problem because the stability of the air volume is not important during fan defrosting operation.

Next, the CPU 210 determines whether or not the air temperature Tf near the fan is larger than the second threshold value Tct2 (ST109). In the present embodiment, the outdoor heat exchange temperature Tc detected by the heat exchange temperature sensor 75 is read as the air temperature Tf near the fan, so that the outdoor heat exchange temperature Tc detected by the heat exchange temperature sensor 75 is the second threshold value Tct2. Determine if it is greater than. The second threshold value Tct2 (unit: ° C.) is a temperature lower than the first threshold value Tct1 and is determined in advance by a test or the like and stored in the storage unit 220 of the outdoor unit control means 200. It is the temperature (for example, 0 ° C.) of the outdoor heat exchanger 23 in which the air temperature in the vicinity is considered to be below the freezing point. When the outdoor heat exchange temperature Tc is not larger than the second threshold value Tct2 (ST109-No), the outdoor heat is reduced even though the rotation speed Rfo of the outdoor fan 27 is lowered and the rotation speed Rc of the compressor 21 is increased. Since the AC temperature Tc is low and the frost generated by the outdoor fan 27 cannot be melted, the CPU 210 proceeds to ST111.

When the outdoor heat exchange temperature Tc is larger than the second threshold value Tct2 (ST109-Yes), the CPU 210 determines whether or not a predetermined time has elapsed from the start of the fan defrosting operation (ST110). The predetermined time is a time (for example, 90 seconds) determined in advance by a test or the like and stored in the storage unit 220 of the outdoor unit control means 200. If a predetermined time has not elapsed from the start of the fan defrosting operation (ST110-No), the CPU 210 continues the fan defrosting operation and returns the process to ST107.

If a predetermined time has elapsed from the start of the fan defrosting operation (ST110-Yes), the CPU 210 restarts the heating operation (ST111). Here, when resuming the operation, the CPU 210 stops the compressor 21 and the outdoor fan 27, switches the four-way valve 22, and puts the refrigerant circuit 10 in the state during the heating operation.

As described above, in the air conditioner 1 of the present embodiment, the outdoor heat exchange temperature is set so that the air temperature Tf near the fan does not become lower than the melting temperature of the frost generated by the outdoor fan 27 during the fan defrosting operation. Since the rotation speed of the outdoor fan 27 and the rotation speed of the compressor 21 are adjusted according to Tc, the frost generated in the outdoor fan 27 can be surely melted in the fan defrosting operation.

In the present embodiment, the outdoor heat exchange temperature Tc is regarded as the air temperature Tf near the fan, and the rotation speed Rfo of the outdoor fan 27 and the rotation speed Rc of the compressor 21 are adjusted according to the outdoor heat exchange temperature Tc. However, the detection value of the temperature detecting means (not shown) installed near the outdoor fan 27 may be set to the air temperature Tf near the fan. In this case, it is desirable that the temperature detecting means be installed on the leeward side of the outdoor heat exchanger 23 and on the leeward side of the outdoor fan 27.

Further, in the present embodiment, as a means for raising the outdoor heat exchange temperature Tc, that is, as a means for raising the outdoor heat exchange temperature, a method of adjusting the rotation speed Rfo of the outdoor fan 27 and the rotation speed Rc of the compressor 21 is adopted. However, it is not limited to this. For example, a heater for heating the outdoor heat exchanger 23 may be separately provided, and the heater may be energized when the outdoor heat exchange temperature Tc becomes equal to or less than the first threshold value.

1 Air conditioner 2 Outdoor unit 3 Indoor unit 21 Compressor 23 Outdoor heat exchanger 24 Expansion valve 27 Outdoor fan 27a Fan motor 31 Indoor heat exchanger 32 Indoor fan 100 Refrigerant circuit 200 Outdoor unit control means 210 CPU
220 Storage unit Rc Compressor rotation speed Rfo Outdoor fan rotation speed Tc Outdoor heat exchange temperature Tct1 1st threshold Tct2 2nd threshold

Claims (3)

A refrigerant circuit in which the refrigerant circulates in the order of the compressor, indoor heat exchanger, expansion valve, and outdoor heat exchanger during heating operation.
A flow path switching means provided in the refrigerant circuit to switch the flow direction of the refrigerant discharged from the compressor, and
An outdoor fan that blows air to the outdoor heat exchanger,
It has an outdoor heat exchange temperature detecting means for detecting the outdoor heat exchange temperature, which is the temperature of the outdoor heat exchanger.
During the heating operation, the outdoor fan is stopped and the flow path switching means is switched to direct the refrigerant discharged from the compressor to the outdoor heat exchanger, and the heat exchange defrosting operation and the heat exchange defrosting operation. After the operation is completed, the control means for performing the fan defrosting operation of driving the outdoor fan to defrost the outdoor fan while keeping the refrigerant discharged from the compressor facing the outdoor heat exchanger. When,
It is an air conditioner with
The control means
During the fan defrosting operation, when the temperature near the fan, which is the temperature of the air near the outdoor fan, becomes equal to or less than the first threshold value, the outdoor heat exchange temperature rise control for raising the temperature of the outdoor heat exchanger is performed.
An air conditioner that features that. The air temperature near the fan is the outdoor heat exchange temperature.
The air conditioner according to claim 1. The control means
During the fan defrosting operation, when the air temperature in the vicinity of the fan becomes equal to or lower than the second threshold value lower than the first threshold value, the fan defrosting operation is terminated.
The air conditioner according to claim 1 or 2.

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